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Copyright (c) 2020 The Khronos Group Inc.
Use of this source code is governed by an MIT-style license that can be
found in the LICENSE.txt file.
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<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>WebGL OES_draw_buffers_indexed Conformance Tests</title>
<LINK rel="stylesheet" href="../../resources/js-test-style.css"/>
<script src="../../js/js-test-pre.js"></script>
<script src="../../js/webgl-test-utils.js"></script>
</head>
<body>
<div id="description"></div>
<div id="console"></div>
<script>
"use strict";
description("This test verifies the functionality of the OES_draw_buffers_indexed extension, if it is available.");

debug("");

var wtu = WebGLTestUtils;
var canvas = document.getElementById("canvas");
var gl = wtu.create3DContext(null, null, 2);
var ext;

const vs = `#version 300 es
layout(location=0) in vec4 vPosition;
void main()
{
    gl_Position = vPosition;
}
`;

const fs = `#version 300 es
precision lowp float;
layout(location = 0) out vec4 o_color0;
layout(location = 1) out vec4 o_color1;
void main()
{
    o_color0 = vec4(1, 0, 0, 0);
    o_color1 = vec4(1, 0, 0, 0);
}
`;

function setup() {
    const program = wtu.setupProgram(gl, [vs, fs]);
    gl.useProgram(program);
    wtu.setupUnitQuad(gl, 0);
    wtu.glErrorShouldBe(gl, 0, 'No errors from program');

    const tex1 = gl.createTexture();
    gl.bindTexture(gl.TEXTURE_2D, tex1);
    gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, 1, 1, 0, gl.RGBA, gl.UNSIGNED_BYTE, null);
    wtu.glErrorShouldBe(gl, 0, 'Create texture 1 successfully');

    const tex2 = gl.createTexture();
    gl.bindTexture(gl.TEXTURE_2D, tex2);
    gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, 1, 1, 0, gl.RGBA, gl.UNSIGNED_BYTE, null);
    wtu.glErrorShouldBe(gl, 0, 'Create texture 2 successfully');

    const attachments = [gl.COLOR_ATTACHMENT0, gl.COLOR_ATTACHMENT1];

    const fb = gl.createFramebuffer();
    gl.bindFramebuffer(gl.FRAMEBUFFER, fb);
    gl.framebufferTexture2D(gl.FRAMEBUFFER, attachments[0], gl.TEXTURE_2D, tex1, 0);
    gl.framebufferTexture2D(gl.FRAMEBUFFER, attachments[1], gl.TEXTURE_2D, tex2, 0);
    shouldBe('gl.checkFramebufferStatus(gl.FRAMEBUFFER)', 'gl.FRAMEBUFFER_COMPLETE');

    gl.drawBuffers(attachments);
    wtu.glErrorShouldBe(gl, 0, 'Set draw buffers without errors');
}

function enableDisableTest() {
    debug("Testing enableiOES/disableiOES");

    // Invalid input
    ext.enableiOES(gl.DEPTH_TEST, 0);
    wtu.glErrorShouldBe(gl, gl.INVALID_ENUM, 'target could only be gl.BLEND');

    ext.disableiOES(gl.DEPTH_TEST, 0);
    wtu.glErrorShouldBe(gl, gl.INVALID_ENUM, 'target could only be gl.BLEND');

    gl.disable(gl.BLEND);

    // Valid input
    ext.enableiOES(gl.BLEND, 0);
    shouldBe('gl.isEnabled(gl.BLEND)', 'true');
    ext.disableiOES(gl.BLEND, 0);
    ext.enableiOES(gl.BLEND, 1);
    shouldBe('gl.isEnabled(gl.BLEND)', 'false');
    gl.enable(gl.BLEND);
    shouldBe('gl.isEnabled(gl.BLEND)', 'true');
    wtu.glErrorShouldBe(gl, 0, 'No errors from enable and disable draw buffers blend state');
}

function constantAlphaBlendColorValidationTest() {
    debug("Testing CONSTANT_COLOR/ALPHA blend functions limit validation");
    function isConstantColorAndAlphaBlendFunctions(first, second)
    {
        return (first == gl.CONSTANT_COLOR || first == gl.ONE_MINUS_CONSTANT_COLOR) &&
            (second == gl.CONSTANT_ALPHA || second == gl.ONE_MINUS_CONSTANT_ALPHA);
    }

    function checkBlendFunctions(src, dst)
    {
        if (isConstantColorAndAlphaBlendFunctions(src, dst) ||
            isConstantColorAndAlphaBlendFunctions(dst, src))
        {
            wtu.glErrorShouldBe(gl, gl.INVALID_OPERATION, 'invalid combinations');
            return false;
        }
        else
        {
            wtu.glErrorShouldBe(gl, 0, 'No error');
            return true;
        }
    }

    const srcFunc = [
        gl.ZERO,
        gl.ONE,
        gl.SRC_COLOR,
        gl.ONE_MINUS_SRC_COLOR,
        gl.DST_COLOR,
        gl.ONE_MINUS_DST_COLOR,
        gl.SRC_ALPHA,
        gl.ONE_MINUS_SRC_ALPHA,
        gl.DST_ALPHA,
        gl.ONE_MINUS_DST_ALPHA,
        gl.CONSTANT_COLOR,
        gl.ONE_MINUS_CONSTANT_COLOR,
        gl.CONSTANT_ALPHA,
        gl.ONE_MINUS_CONSTANT_ALPHA,
        gl.SRC_ALPHA_SATURATE,
    ];

    const dstFunc = [
        gl.ZERO,           gl.ONE,
        gl.SRC_COLOR,      gl.ONE_MINUS_SRC_COLOR,
        gl.DST_COLOR,      gl.ONE_MINUS_DST_COLOR,
        gl.SRC_ALPHA,      gl.ONE_MINUS_SRC_ALPHA,
        gl.DST_ALPHA,      gl.ONE_MINUS_DST_ALPHA,
        gl.CONSTANT_COLOR, gl.ONE_MINUS_CONSTANT_COLOR,
        gl.CONSTANT_ALPHA, gl.ONE_MINUS_CONSTANT_ALPHA,
    ];

    let src, dst;

    // CONSTANT_COLOR/ALPHA invalid combination check
    for (let i = 0, leni = srcFunc.length; i < leni; i++)
    {
        src = srcFunc[i];
        for (let j = 0, lenj = dstFunc.length; j < lenj; j++)
        {
            dst = dstFunc[j];
            ext.blendFunciOES(0, src, dst);
            checkBlendFunctions(src, dst);
            ext.blendFuncSeparateiOES(0, src, dst, gl.ONE, gl.ONE);
            checkBlendFunctions(src, dst);
        }
    }
}

function indexedBlendColorTest() {
    debug('');
    debug("Testing blendEquationiOES and blendFunciOES");
    wtu.glErrorShouldBe(gl, 0, 'top of indexedBlendColorTest');

    gl.clearColor(0, 0, 1, 1);
    gl.clear(gl.COLOR_BUFFER_BIT);

    ext.blendEquationiOES(0, gl.FUNC_ADD);
    ext.blendFunciOES(0, gl.ONE, gl.ONE);
    ext.blendEquationiOES(1, gl.FUNC_ADD);
    ext.blendFunciOES(1, gl.SRC_ALPHA, gl.ONE_MINUS_SRC_ALPHA);
    gl.drawArrays(gl.TRIANGLES, 0, 6);
    wtu.glErrorShouldBe(gl, 0, 'Draw quad without errors');

    gl.readBuffer(gl.COLOR_ATTACHMENT0);
    wtu.checkCanvasRect(gl, 0, 0, 1, 1, [255, 0, 255, 255]);

    gl.readBuffer(gl.COLOR_ATTACHMENT1);
    wtu.checkCanvasRect(gl, 0, 0, 1, 1, [0, 0, 255, 255]);

    debug("Testing blendEquationSeparateiOES and blendFuncSeparateiOES");
    gl.clear(gl.COLOR_BUFFER_BIT);

    ext.blendEquationSeparateiOES(0, gl.FUNC_ADD, gl.FUNC_SUBTRACT);
    ext.blendFuncSeparateiOES(0, gl.ONE, gl.ONE, gl.ZERO, gl.ZERO);
    ext.blendEquationSeparateiOES(1, gl.FUNC_ADD, gl.FUNC_SUBTRACT);
    ext.blendFuncSeparateiOES(1, gl.SRC_ALPHA, gl.ONE_MINUS_SRC_ALPHA, gl.ZERO, gl.ZERO);
    gl.drawArrays(gl.TRIANGLES, 0, 6);
    wtu.glErrorShouldBe(gl, 0, 'Draw quad without errors');

    gl.readBuffer(gl.COLOR_ATTACHMENT0);
    wtu.checkCanvasRect(gl, 0, 0, 1, 1, [255, 0, 255, 0]);

    gl.readBuffer(gl.COLOR_ATTACHMENT1);
    wtu.checkCanvasRect(gl, 0, 0, 1, 1, [0, 0, 255, 0]);

    debug("Testing colorMaskiOES");
    gl.clear(gl.COLOR_BUFFER_BIT);
    ext.colorMaskiOES(0, false, false, false, false);
    ext.colorMaskiOES(1, true, true, true, true);

    gl.drawArrays(gl.TRIANGLES, 0, 6);
    wtu.glErrorShouldBe(gl, 0, 'Draw quad without errors');

    gl.readBuffer(gl.COLOR_ATTACHMENT0);
    wtu.checkCanvasRect(gl, 0, 0, 1, 1, [0, 0, 255, 255]);

    gl.readBuffer(gl.COLOR_ATTACHMENT1);
    wtu.checkCanvasRect(gl, 0, 0, 1, 1, [0, 0, 255, 0]);

    debug('');
    debug(`Testing that new tokens aren't on the extension.`);
    shouldBe('ext.BLEND_EQUATION_RGB', 'undefined');
    shouldBe('ext.BLEND_EQUATION_ALPHA', 'undefined');
    shouldBe('ext.BLEND_SRC_RGB', 'undefined');
    shouldBe('ext.BLEND_SRC_ALPHA', 'undefined');
    shouldBe('ext.BLEND_DST_RGB', 'undefined');
    shouldBe('ext.BLEND_DST_ALPHA', 'undefined');
    shouldBe('ext.COLOR_WRITEMASK', 'undefined');

    debug("Testing new tokens for getIndexedParameterTest");
    shouldBe('gl.getIndexedParameter(gl.BLEND_EQUATION_RGB, 0)', 'gl.FUNC_ADD');
    shouldBe('gl.getIndexedParameter(gl.BLEND_EQUATION_ALPHA, 0)', 'gl.FUNC_SUBTRACT');
    shouldBe('gl.getIndexedParameter(gl.BLEND_SRC_RGB, 0)', 'gl.ONE');
    shouldBe('gl.getIndexedParameter(gl.BLEND_DST_RGB, 0)', 'gl.ONE');
    shouldBe('gl.getIndexedParameter(gl.BLEND_SRC_ALPHA, 0)', 'gl.ZERO');
    shouldBe('gl.getIndexedParameter(gl.BLEND_DST_ALPHA, 0)', 'gl.ZERO');
    shouldBe('gl.getIndexedParameter(gl.BLEND_EQUATION_RGB, 1)', 'gl.FUNC_ADD');
    shouldBe('gl.getIndexedParameter(gl.BLEND_EQUATION_ALPHA, 1)', 'gl.FUNC_SUBTRACT');
    shouldBe('gl.getIndexedParameter(gl.BLEND_SRC_RGB, 1)', 'gl.SRC_ALPHA');
    shouldBe('gl.getIndexedParameter(gl.BLEND_DST_RGB, 1)', 'gl.ONE_MINUS_SRC_ALPHA');
    shouldBe('gl.getIndexedParameter(gl.BLEND_SRC_ALPHA, 1)', 'gl.ZERO');
    shouldBe('gl.getIndexedParameter(gl.BLEND_DST_ALPHA, 1)', 'gl.ZERO');

    shouldBe('gl.getIndexedParameter(gl.COLOR_WRITEMASK, 0)', '[false, false, false, false]');
    shouldBe('gl.getIndexedParameter(gl.COLOR_WRITEMASK, 1)', '[true, true, true, true]');

    debug("Testing non-indexed getParamter get state from draw buffer 0");
    shouldBe('gl.getParameter(gl.BLEND_SRC_RGB)', 'gl.ONE');
    shouldBe('gl.getParameter(gl.BLEND_DST_RGB)', 'gl.ONE');
    shouldBe('gl.getParameter(gl.BLEND_SRC_ALPHA)', 'gl.ZERO');
    shouldBe('gl.getParameter(gl.BLEND_DST_ALPHA)', 'gl.ZERO');
    shouldBe('gl.getParameter(gl.BLEND_EQUATION_RGB)', 'gl.FUNC_ADD');
    shouldBe('gl.getParameter(gl.BLEND_EQUATION_ALPHA)', 'gl.FUNC_SUBTRACT');
    shouldBe('gl.getParameter(gl.COLOR_WRITEMASK)', '[false, false, false, false]');

    debug("Testing non-indexed calls modify all draw buffers state");
    gl.blendEquationSeparate(gl.FUNC_SUBTRACT, gl.FUNC_ADD);
    gl.blendFuncSeparate(gl.ONE_MINUS_DST_ALPHA, gl.DST_ALPHA, gl.ONE, gl.ONE);
    gl.colorMask(true, false, true, false);
    wtu.glErrorShouldBe(gl, 0, 'Non-indexed state set without errors');

    shouldBe('gl.getParameter(gl.BLEND_EQUATION_RGB)', 'gl.FUNC_SUBTRACT');
    shouldBe('gl.getParameter(gl.BLEND_EQUATION_ALPHA)', 'gl.FUNC_ADD');
    shouldBe('gl.getParameter(gl.BLEND_SRC_RGB)', 'gl.ONE_MINUS_DST_ALPHA');
    shouldBe('gl.getParameter(gl.BLEND_DST_RGB)', 'gl.DST_ALPHA');
    shouldBe('gl.getParameter(gl.BLEND_SRC_ALPHA)', 'gl.ONE');
    shouldBe('gl.getParameter(gl.BLEND_DST_ALPHA)', 'gl.ONE');
    shouldBe('gl.getParameter(gl.COLOR_WRITEMASK)', '[true, false, true, false]');

    shouldBe('gl.getIndexedParameter(gl.BLEND_EQUATION_RGB, 0)', 'gl.FUNC_SUBTRACT');
    shouldBe('gl.getIndexedParameter(gl.BLEND_EQUATION_ALPHA, 0)', 'gl.FUNC_ADD');
    shouldBe('gl.getIndexedParameter(gl.BLEND_SRC_RGB, 0)', 'gl.ONE_MINUS_DST_ALPHA');
    shouldBe('gl.getIndexedParameter(gl.BLEND_DST_RGB, 0)', 'gl.DST_ALPHA');
    shouldBe('gl.getIndexedParameter(gl.BLEND_SRC_ALPHA, 0)', 'gl.ONE');
    shouldBe('gl.getIndexedParameter(gl.BLEND_DST_ALPHA, 0)', 'gl.ONE');
    shouldBe('gl.getIndexedParameter(gl.BLEND_EQUATION_RGB, 1)', 'gl.FUNC_SUBTRACT');
    shouldBe('gl.getIndexedParameter(gl.BLEND_EQUATION_ALPHA, 1)', 'gl.FUNC_ADD');
    shouldBe('gl.getIndexedParameter(gl.BLEND_SRC_RGB, 1)', 'gl.ONE_MINUS_DST_ALPHA');
    shouldBe('gl.getIndexedParameter(gl.BLEND_DST_RGB, 1)', 'gl.DST_ALPHA');
    shouldBe('gl.getIndexedParameter(gl.BLEND_SRC_ALPHA, 1)', 'gl.ONE');
    shouldBe('gl.getIndexedParameter(gl.BLEND_DST_ALPHA, 1)', 'gl.ONE');

    shouldBe('gl.getIndexedParameter(gl.COLOR_WRITEMASK, 0)', '[true, false, true, false]');
    shouldBe('gl.getIndexedParameter(gl.COLOR_WRITEMASK, 1)', '[true, false, true, false]');
}

function runTestExtension() {
    setup();

    testInvalidValues();

    enableDisableTest();

    // blending should be enabled for drawBuffers 0 and 1 at this point

    constantAlphaBlendColorValidationTest();

    indexedBlendColorTest();

    testColorMaskDrawNoOp();
}

function runInvalidEnumsTest() {
    debug("Testing new enums for getIndexedParameterTest being invalid before requesting the extension");
    gl.getIndexedParameter(0x8009, 0);  // BLEND_EQUATION_RGB
    wtu.glErrorShouldBe(gl, gl.INVALID_ENUM, 'BLEND_EQUATION_RGB');
    gl.getIndexedParameter(0x883D, 0);  // BLEND_EQUATION_ALPHA
    wtu.glErrorShouldBe(gl, gl.INVALID_ENUM, 'BLEND_EQUATION_ALPHA');
    gl.getIndexedParameter(0x80C9, 0);  // BLEND_SRC_RGB
    wtu.glErrorShouldBe(gl, gl.INVALID_ENUM, 'BLEND_SRC_RGB');
    gl.getIndexedParameter(0x80CB, 0);  // BLEND_SRC_ALPHA
    wtu.glErrorShouldBe(gl, gl.INVALID_ENUM, 'BLEND_SRC_ALPHA');
    gl.getIndexedParameter(0x80C8, 0);  // BLEND_DST_RGB
    wtu.glErrorShouldBe(gl, gl.INVALID_ENUM, 'BLEND_DST_RGB');
    gl.getIndexedParameter(0x80CA, 0);  // BLEND_DST_ALPHA
    wtu.glErrorShouldBe(gl, gl.INVALID_ENUM, 'BLEND_DST_ALPHA');
    gl.getIndexedParameter(0x0C23, 0);  // COLOR_WRITEMASK
    wtu.glErrorShouldBe(gl, [gl.INVALID_OPERATION, gl.INVALID_ENUM], 'invalid operations or invalid enums for COLOR_WRITEMASK');
}

function testInvalidValues() {
    const numDrawBuffers = gl.getParameter(gl.MAX_DRAW_BUFFERS);
    if (!numDrawBuffers) throw new Error('!numDrawBuffers');
    wtu.shouldGenerateGLError(gl, gl.INVALID_VALUE, `ext.enableiOES(gl.BLEND, -1)`);
    wtu.shouldGenerateGLError(gl, gl.INVALID_VALUE, `ext.enableiOES(gl.BLEND, ${numDrawBuffers})`);
    wtu.shouldGenerateGLError(gl, 0, `ext.enableiOES(gl.BLEND, ${numDrawBuffers-1})`);

    wtu.shouldGenerateGLError(gl, gl.INVALID_VALUE, `ext.disableiOES(gl.BLEND, -1)`);
    wtu.shouldGenerateGLError(gl, gl.INVALID_VALUE, `ext.disableiOES(gl.BLEND, ${numDrawBuffers})`);
    wtu.shouldGenerateGLError(gl, 0, `ext.disableiOES(gl.BLEND, ${numDrawBuffers-1})`);

    wtu.shouldGenerateGLError(gl, gl.INVALID_VALUE, `ext.blendEquationiOES(-1, gl.FUNC_ADD)`);
    wtu.shouldGenerateGLError(gl, gl.INVALID_VALUE, `ext.blendEquationiOES(${numDrawBuffers}, gl.FUNC_ADD)`);
    wtu.shouldGenerateGLError(gl, 0, `ext.blendEquationiOES(${numDrawBuffers-1}, gl.FUNC_ADD)`);

    wtu.shouldGenerateGLError(gl, gl.INVALID_VALUE, `ext.blendEquationSeparateiOES(-1, gl.FUNC_ADD, gl.FUNC_ADD)`);
    wtu.shouldGenerateGLError(gl, gl.INVALID_VALUE, `ext.blendEquationSeparateiOES(${numDrawBuffers}, gl.FUNC_ADD, gl.FUNC_ADD)`);
    wtu.shouldGenerateGLError(gl, 0, `ext.blendEquationSeparateiOES(${numDrawBuffers-1}, gl.FUNC_ADD, gl.FUNC_ADD)`);

    wtu.shouldGenerateGLError(gl, gl.INVALID_VALUE, `ext.blendFunciOES(-1, gl.ONE, gl.ONE)`);
    wtu.shouldGenerateGLError(gl, gl.INVALID_VALUE, `ext.blendFunciOES(${numDrawBuffers}, gl.ONE, gl.ONE)`);
    wtu.shouldGenerateGLError(gl, 0, `ext.blendFunciOES(${numDrawBuffers-1}, gl.ONE, gl.ONE)`);

    wtu.shouldGenerateGLError(gl, gl.INVALID_VALUE, `ext.blendFuncSeparateiOES(-1, gl.ONE, gl.ZERO, gl.ONE, gl.ZERO)`);
    wtu.shouldGenerateGLError(gl, gl.INVALID_VALUE, `ext.blendFuncSeparateiOES(${numDrawBuffers}, gl.ONE, gl.ZERO, gl.ONE, gl.ZERO)`);
    wtu.shouldGenerateGLError(gl, 0, `ext.blendFuncSeparateiOES(${numDrawBuffers-1}, gl.ONE, gl.ZERO, gl.ONE, gl.ZERO)`);

    wtu.shouldGenerateGLError(gl, gl.INVALID_VALUE, `ext.colorMaskiOES(-1, 1,1,1,1)`);
    wtu.shouldGenerateGLError(gl, gl.INVALID_VALUE, `ext.colorMaskiOES(${numDrawBuffers}, 1,1,1,1)`);
    wtu.shouldGenerateGLError(gl, 0, `ext.colorMaskiOES(${numDrawBuffers-1}, 1,1,1,1)`);
}

function* range(n) {
  for (let i = 0; i < n; i++) {
    yield i;
  }
}

function testColorMaskDrawNoOp() {
    debug('');
    debug('testColorMaskDrawNoOp')
    // > If any draw buffer with an attachment does not have a defined
    //   fragment shader output, draws generate INVALID_OPERATION,
    //   unless all 4 channels of colorMask are set to false.
    const NUM_OUTPUTS = gl.getParameter(gl.MAX_COLOR_ATTACHMENTS);
    shouldBeTrue(`${NUM_OUTPUTS} > 1`);

    const fb = gl.createFramebuffer();
    gl.bindFramebuffer(gl.FRAMEBUFFER, fb);
    gl.viewport(0,0,1,1);

    const DRAW_BUFFERS = [];
    for (const i of range(NUM_OUTPUTS)) {
        const tex = gl.createTexture();
        gl.bindTexture(gl.TEXTURE_2D, tex);
        gl.texStorage2D(gl.TEXTURE_2D, 1, gl.RGBA8, 1, 1);
        const ca = gl.COLOR_ATTACHMENT0+i;
        DRAW_BUFFERS.push(ca)
        gl.framebufferTexture2D(gl.FRAMEBUFFER, ca,
                                gl.TEXTURE_2D, tex, 0);
    }
    shouldBe('gl.checkFramebufferStatus(gl.FRAMEBUFFER)', 'gl.FRAMEBUFFER_COMPLETE');

    gl.drawBuffers(DRAW_BUFFERS);
    gl.colorMask(1, 1, 1, 1);
    gl.disable(gl.BLEND);

    gl.clearColor(0, 0, 0, 0);
    gl.clear(gl.COLOR_BUFFER_BIT);

    for (const i of range(NUM_OUTPUTS)) {
        gl.readBuffer(gl.COLOR_ATTACHMENT0+i);
        wtu.checkCanvasRect(gl, 0, 0, 1, 1, [0, 0, 0, 0], `COLOR_ATTACHMENT${i} initially black`);
    }

    for (const validOutput of range(NUM_OUTPUTS)) {
        const invalidOutput = validOutput ^ 0b11;
        debug(`validOutput: ${validOutput}, invalidOutput: ${invalidOutput}`);
        const prog = wtu.setupProgram(gl, [
            `\
#version 300 es
void main() {
    gl_Position = vec4(0,0,0,1);
    gl_PointSize = 1.0f;
}
`,
            `\
#version 300 es
precision mediump float;
layout(location=${validOutput}) out vec4 o_color;
void main() {
    o_color = vec4(1,1,1,1);
}
`
        ]);
        gl.useProgram(prog);

        wtu.glErrorShouldBe(gl, gl.NO_ERROR,
            'After init.');

        gl.colorMask(1,1,1,1);
        gl.drawBuffers(DRAW_BUFFERS);
        gl.drawArrays(gl.POINTS, 0, 1);
        wtu.glErrorShouldBe(gl, gl.INVALID_OPERATION,
            'Drawing with unmasked undefined color outputs.');

        gl.colorMask(0,0,0,0);
        gl.drawBuffers(DRAW_BUFFERS);
        gl.drawArrays(gl.POINTS, 0, 1);
        wtu.glErrorShouldBe(gl, gl.NO_ERROR,
            'Drawing with colorMask-masked-out undefined color outputs.');

        gl.colorMask(1,1,1,1);
        gl.drawBuffers(DRAW_BUFFERS.map((x,i) => (i == invalidOutput) ? x : 0));
        gl.drawArrays(gl.POINTS, 0, 1);
        wtu.glErrorShouldBe(gl, gl.INVALID_OPERATION,
            'Drawing with wrong-id drawBuffer-masked-out undefined color outputs.');

        gl.drawBuffers(DRAW_BUFFERS.map((x,i) => (i == validOutput) ? x : 0));
        gl.drawArrays(gl.POINTS, 0, 1);
        wtu.glErrorShouldBe(gl, gl.NO_ERROR,
            'Drawing with drawBuffer-masked-out undefined color outputs.');

        gl.colorMask(0,0,0,0);
        gl.drawBuffers([]);
        gl.drawArrays(gl.POINTS, 0, 1);
        wtu.glErrorShouldBe(gl, gl.NO_ERROR,
            'Drawing with colorMask+drawBuffer-masked-out undefined color outputs.');

        const testMask = (r,g,b,a) => {
            debug(`testMask(${[r,g,b,a]})`);
            gl.drawBuffers(DRAW_BUFFERS);

            gl.colorMask(1,1,1,1);
            gl.clearColor(0, 0, 0, 0);
            gl.clear(gl.COLOR_BUFFER_BIT);
            gl.colorMask(0,0,0,0);
            ext.colorMaskiOES(validOutput, r,g,b,a);
            gl.drawArrays(gl.POINTS, 0, 1);
            wtu.glErrorShouldBe(gl, gl.NO_ERROR,
                `Drawing with sole defined color${validOutput} output writemask: ${[r,g,b,a]}.`);

            for (const i of range(NUM_OUTPUTS)) {
                gl.readBuffer(gl.COLOR_ATTACHMENT0+i);
                let expect = [0,0,0,0];
                if (i == validOutput) {
                    expect = [r,g,b,a].map(x => 0xff*x);
                }
                wtu.checkCanvasRect(gl, 0, 0, 1, 1, expect, `COLOR_ATTACHMENT${i}: [${expect}]`);
            }

            gl.colorMask(1,1,1,1);
            gl.clearColor(0, 0, 0, 0);
            gl.clear(gl.COLOR_BUFFER_BIT);
            gl.colorMask(r,g,b,a);
            for (const i of range(NUM_OUTPUTS)) {
                if (i == validOutput) continue;
                ext.colorMaskiOES(i, 0,0,0,0);
            }
            gl.drawArrays(gl.POINTS, 0, 1);
            wtu.glErrorShouldBe(gl, gl.NO_ERROR,
                `Drawing with sole remaining defined color${validOutput} output writemask: ${[r,g,b,a]}.`);

            for (const i of range(NUM_OUTPUTS)) {
                gl.readBuffer(gl.COLOR_ATTACHMENT0+i);
                let expect = [0,0,0,0];
                if (i == validOutput) {
                    expect = [r,g,b,a].map(x => 0xff*x);
                }
                wtu.checkCanvasRect(gl, 0, 0, 1, 1, expect, `COLOR_ATTACHMENT${i}: [${expect}]`);
            }

            if (r || g || b || a) {
                gl.colorMask(0,0,0,0);
                ext.colorMaskiOES(invalidOutput, r,g,b,a);
                gl.drawArrays(gl.POINTS, 0, 1);
                wtu.glErrorShouldBe(gl, gl.INVALID_OPERATION,
                    `Drawing with wrong-id undefined color output color masked: ${[r,g,b,a]}.`);

                gl.drawBuffers([]);
                gl.drawArrays(gl.POINTS, 0, 1);
                wtu.glErrorShouldBe(gl, gl.NO_ERROR,
                    'Drawing with wrong-id colorMask, but all-off drawBuffers.');

                gl.drawBuffers(DRAW_BUFFERS.map((x,i) => (i == validOutput) ? x : 0));
                gl.drawArrays(gl.POINTS, 0, 1);
                wtu.glErrorShouldBe(gl, gl.NO_ERROR,
                    'Drawing with wrong-id colorMask, but right-id drawBuffers masked.');
            }
        };

        testMask(0,0,0,0);
        testMask(1,0,0,0);
        testMask(0,1,0,0);
        testMask(0,0,1,0);
        testMask(0,0,0,1);
        testMask(1,1,1,1);
    }
}

function runTest() {
  if (!gl) {
    testFailed("context does not exist");
  } else {
    testPassed("context exists");

    runInvalidEnumsTest();

    ext = gl.getExtension("OES_draw_buffers_indexed");

    wtu.runExtensionSupportedTest(gl, "OES_draw_buffers_indexed", ext !== null);

    if (ext !== null) {
      runTestExtension();
    } else {
      testPassed("No OES_draw_buffers_indexed support -- this is legal");
    }
  }
}

runTest();

var successfullyParsed = true;
</script>
<script src="../../js/js-test-post.js"></script>
</body>
</html>
